Current techniques for coloring ceramics have limitations due to processing. At present, methods involve dipping a pre-sintered ceramic body into a coloring solution containing metallic salts. Such methods may often result in inhomogeneous coloring on the surface of the ceramic. In addition, the penetration of the coloring solution into the pores of the ceramic is largely affected by the components, composition, and properties of the solution. Depending on the constituents present in the solution, little or no color penetration can result.
Such disadvantages arise when attempting to color a pre-sintered ceramic. This has prompted the need for an alternative method to color a ceramic body. Such a method will remove the need to color a pre-sintered ceramic body and will result in a ceramic with innate color aesthetics that are homogenous throughout the ceramic both internally and on the surface. The present invention relates to creating a colored ceramic during a slip casting process in which a color solution consisting of metallic salts is introduced into the slip and subsequently combined with a binder, dried, pressed into a green state and sintered.
Current methods for coloring ceramic bodies involve dipping a pre-sintered ceramic of final shape into a coloring liquid. These processes require a wide range of soaking times and drying times to ensure uniform and good quality results. After dipping, the ceramic body is dried and sintered, after which the final color is achieved.
The dipping methods currently used depend largely on the capillary action of the coloring liquid and the infiltration of said liquid into ceramic pores. The properties of the coloring liquid, such as composition, concentration, viscosity, pH, surface tension and wetting ability directly influence the performance of the liquid. Should any property not be optimized, undesirable results such as disproportionate coloring or poor penetration of color into the ceramic body may result.
These methods color ceramic bodies after the ceramic has already been processed and fabricated. The coloring agent is added to the ceramic system after initial fabrication of the ceramic. Therefore, the color is not innate to the ceramic.